Carbonyldiphosphonates



United States Patent O 3,497,313 CARBONYLDIPHOSPHONATES Oscar T. Quimby, Colerain Township, Hamilton County, Ohio, assignor to The Procter & Gamble Company, Cincinnati, Ohio, a corporation of Ohio No Drawing. Filed Dec. 29, 1966, Ser. No. 605,606 Int. Cl. C01b 25/16, 31/00; C07f 9/ 28 US. Cl. 23-50 2 Claims ABSTRACT OF THE DISCLOSURE Carbonyldiphosphonate salts, =C(PO M can be made by alkaline hydrolysis of a salt of a dihalomethylenediphosphonic acid, X C(PO M The salts thus made are useful (1) as metal ion complexing agents, (2) as intermediates for the production of methanehydroxydiphosphonates, HOCH(PO M and (3) as detergency builders.

BACKGROUND OF THE INVENTION This invention relates to carbonyldiphosphonates, particularly carbonyldiphosphonate salts, and to a process for making carbonyldiphosphonates. This invention also relates to the use of carbonyldiphosphonates as metal ion complexing agents, as chemical intermediates, and as socalled builder materials to enhance the cleaning capacity of detergent compounds.

Some molecules and ions have the property of being able to replace water molecules surrounding a metal ion. When this occurs, the resulting substance is cal ed a metal complex, or metal coordination compound. The group which replaces the water molecules and combines with the metal ion is called a ligand, or metal ion complexing agent. The principles and applications of metal ion complexing and metal ion complexing agents are discussed in Organic sequestering Agents, by Stanley Chaberek and Arthur E. Martell (John Wiley & Sons, Inc., New York, 1959).

SUMMARY OF THE INVENTION Salts of carbonyldiphosphonic acid can be made by alkaline hydrolysis of a salt of dihalomethylenediphosphonic acid. Carbonyldiphosphonates are unexpectedly efficient as metal ion complexing agents, particularly in weakly alkaline aqueous solutions, and also unexpectedly stable to hydrolysis. They are also useful as precursors of n1ethanehydroxydiphosphonates, and as detergency builder compounds which are more stable to hydrolysis in aque ous solutions than previously known, widely used builders.

DETAILED DESCRIPTION It should be understood that the detailed description and specific examples which follow, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent from this detailed description to those skilled in the art.

(A) Preparation of carbonyldiphosphonates In 1957, M. I. Kabachnik et al. reported (Izvest. Akad. Nauk S.S.S.R. Otdel, Khim Nauk 1957, 48-53; Chem. Abstr. 51, 10366h-67b (1957)) that tetramethyl carbonyldiphospho-nate could be obtained by reacting phosgene with P(OCH Repetition of the experiments showed that the compound had not in fact been formed, and a retraction was published in 1958 (same authors and journal 1958, 1395-96; Chem. Abstr. 53, 6988c (1959)).

It has been found that salts of carbonyldiphosphonic acid can be prepared by hydrolyzing a salt of a dihalomethylenediphosphonic acid, for example the tetrasodium ICC salt of dichloroor dibromomethylenediphosphonic acid, with a strong base, such as sodium, potassium, ammonium, or tetramethylammonium hydroxide. It is preferred that the base used be free from polyvalent cations such as calcium and magnesium, however, since these can cause undesired, hard-to-remove impurities. Any base which is strong enough to maintain an alkaline pH is suitable, however, if it does not introduce unwanted materials. Even alkaline salts such as alkali metal carbonate, silicate, or orthophosphate can be used, if the impurities thereby introduced are not objectionable.

The typical reaction sequence is represented by the following equations, in which X represents a halide radical, such as chloride or bromide, and M represents a cation selected from the group consisting of sodium, potassium, ammonium, and substituted ammonium:

The reaction mixture should not be allowed to stand for any substantial length of time at a pH below 4, or some carbonphosphorus bonds will be hydrolyzed. If the pH falls below about 10, the eaction will slow down. Excess base avoids these dangers. The dibromo anion, Br C(PO hydrolyzes somewhat faster than the dichloro, Cl C (PO The last reaction given above is an equilibrium which tends to go toward the right with increasing pH and toward the left with decreasing pH.

This synthesis is illustrated by the following example:

EXAMPLE -1 Fifty grams (0.2 moles) of 98% pure Cl C(PO Na 48 grams of NaOl-I (1.2 moles), and 175 milliliters of water were refluxed for 6 hours, then allowed to cool slowly. About ten hours later, 125 milliliters of acetone was added dropwise over a minute period. The suspension was heated to reflux (about 60 C.), and again cooled to room temperature. After cooling for about an hour, the suspension was digested for an additional hour at room temperature. The sample was filtered, and the crystals were washed first with milliliters of 50% acetone -50% water, and then with 150 milliliters of acetone, and dried. In this example, the pH of the reaction mixture did not fall below 12. The yield was 60.3 grams of crude product, purified to yield 29.8 grams of PO3N32 2 The product was identified by elemental analysis and P nuclear magnetic resonance spectra.

The temperature at which the above reaction is carried out can be varied between room temperature (about 20 C.) and about 150 0., preferably between about 50 C. and C. At lower temperatures the reaction proceeds very slowly, however, and the temperature of aqueous refluxing (about 100-105 C.) is convenient and effective. If the temperature is made too high, on the other hand, side reactions will compete with the main reaction and destroy some of the product. If the reaction is carried out in boiling water, no mixing or stirring is required.

The amount of base used may be varied widely. If the dihalomethylenediphosphonate is heated even by itself, hydrolysis begins in a few minutes at 90 to 100 C. Complete replacement of halide with hydroxyl as shown in the first reaction above requires at least two moles of base per mole of dihalomethylenediphosphonate, however. To avoid hydrolyzing carbon-phosphorus bonds, and for greater speed and efiiciency in the desired reaction, excess base is desirable. About 6 moles of base per mole of dihalomethylenediphosphonate is sufficient for this purpose, although more can be used if desired. Reaction time can be varied from about 5 minutes to 12 hours or more, depending on the temperature of hydrolysis. In the example above, the reaction was essentially complete in about half an hour or less, but heating was continued to insure complete reaction.

Other salts, for example the disodium and trisodium salts, O=C(PO NaH) and O=C(PO Na H, can be prepared in solution in similar fashions. It is not necessary to isolate the salt as a solid for many applications.

The dihalomethylenediphosphonate starting material can be prepared in a variety of ways, for example from the esters of methylenediphosphonate and halogen or sodium hypohalite. Synthesis of dihalomethylenediph-osphonates is described in the copending patent application Ser. No. 587,417, filed on Oct. 18, 1966, by Oscar T. Quimby et al. and now abandoned.

(B) Utility of carbonyldiphosphonates Car-bonyldiphosphonates find utility (1) as metal ion complexing agents; (2) as intermediates for the production of methane-hydroxydiphosphonates, which are valuable builders in cleansing and laundering compositions; and ("3) as builders, themselves, in cleansing and laundering compositions.

Hereafter in this specification the carbonyldiphosphonate compounds are conveniently referred to as CDP. This expression is intended to cover the acid as well as the various neutralized and partially neutralized salt forms, unless otherwise specified.

(1) Metal ion complexing agents.It has been found that CDP compounds, when added to aqueous solutions containing metal ions, function very well as metal ion complexing agents, particularly for polyvalent metal ions, CDP is especially effective in forming complexes of hivalent and trivalent metal ions, for example aluminum, calcium, copper, iron, magnesium and zinc ions. The pure or refined, compounds as well as mixtures, or crude compounds can be employed. For example, they are well suited for binding calcium ions to a large extent and, hence, can be used especially for water-softening purposes.

For practical purposes, other applications also are feasible. For instance, textiles can be freed from encrustations due to the deposition of alkaline earth salts. Textiles which had been Washed with soap or pyrophosphatecontaining agents can be treated with the above-named compounds in order to decrease the ash content. In cleansing processes, particularly bottle washing, the use of the compounds according to the invention avoids the pre- CipitatiOn of calcite or other slightly soluble calcium salts.

The capability of CDP to form complexes also can be utilized to good advantage in systems wherein copper ions have an undesirable effect. As an example, the avoidance of decomposition of per-compounds by copper ions is named. The compounds according to the invention also can well serve as additives to dye baths for textiles to bind metal ions as complexes in order to prevent these metal ions from forming undesirable hues and shades of the color. For these purposes, the use of at least stoichiometrical quantities is required. What constitutes stoichiometrical quantities for the compound employed is easily established by a simple measurement.

Furthermore, the capability of CDP to form complexes with metal ions can be used for the supply of trace elements to plants.

While in many applications a wide variety of concentrations of metal ion complexing agents may be employed, concentrations ranging from 1 mole of carbonyldiphosphonate per 5000 moles of metal ions to stoichiometrical quantities are preferred.

The use of carbonyldiphosphonate salts as metal ion complexing agents is illustrated by the following example.

EXAMPLE 2 The ability of tWo carbonyldiphosphonate salts to sequester calcium ions was tested by a method essentially the same as that described by R. R. Irani and C. F. Callis 1n J. Phys. Chem. 64, 1389-407 (1960), except that 0.02 M sodium caprate was substituted for oxalate. For comparison, two well known, widely used sequestrants were also tested. Tetrasodium carbonyldiphosphonate, tetrasodium pyrophosphate, and sodium tripolyphosphate were each tested at 0.12% sequestrant concentration, and 0.02 M sodium caprate concentration. The solutions for these three salts were adjusted to pH 8.0, 9.0 10.0, and 11.0 with sodium hydroxide. In the case of tetramethylammonium CDP, sufiicient tetrasodium CDP was weighed out to give a 0.12% solution, but hydrogen was substituted for sodium with an ion exchange column. The solutions of the acid thus obtained were then adjusted to pH 9.0, 10.0, and 11.0 with tetramethylammonium hydroxide. In addition, tetramethylammonium caprate was substituted for sodium caprate, so that there was complete substitution of tetramethylammonium for sodium.

The following table shows the calcium sequestration ability of these salts at various pH levels, measured as the number of grams of calcium sequestered per grams of sequestrant. In the case of tetramethylammonium CDP, the values shown without parentheses are per 100 grams of tetrasodium CDP added. The numbers in parentheses are calculated values for the tetramethylammonium salt basis, obtained by multiplying the corresponding values by the molecular weight ratio 277.9/4826.

*Not tested at pH 8.0.

Although no value was experimentally determined for the effectiveness of tetrasodium pyrophosphate at a pH of 8.0, it is known (and confirmed by the data presented above) that tetrasodium pyrophosphate is less effective than sodium tripolyphosphate at any pH level. It should be noted from the above table that carbonyldiphosphonates are particularly effective in weakly alkaline (pH about 8 or 9) aqueous solutions, when compared to the eifectiveness of other sequestrants. That is to say, lowering pH does not exert as great an adverse eifect on carbonyldiphosphonate as the other sequestrants tested. Thus, while on a weight basis tetramethylammonium carbonyldiphosphonate was substantially less effective than pyrophosphate at pH 10.0 and 11.0, it was more eifective at pH 9.0. Also, while under the conditions of this test sodium tripolyphosphate appeared totally ineffective at pH 8.0, tetrasodium carbonyldiphosphonate appeared to lose less than 50% of its sequestration ability upon reduction of pH from 11.0 to 8.0.

The precipitate formed in these tests was usually calcium caprate monohydrate. However, in the case of tetrasodium carbonyldiphosphonate, the precipitate was a calcium salt of CDP. Substituting tetramethylammonium ions for sodium ions reduces the precipitation of the calcium carbonyldiphosphonate salt, and more accurately represents the sequestering ability of CDP.

(2) Intermediates.-While CDP compounds find utility as metal ion complexing agents, theyare also useful as intermediates for the production of methanehydroxydiphosphonates, which are valuable detergency builders more fully described in the copending application of Oscar T. Quimby, Ser. No. 517,073, filed Dec. 28, 1965. For example, this can be accomplished by hydrogenating CDP according to the following reaction, as an alternate to the method described in the last mentioned copending application:

HOCH(PO3M2)2 preferably at pH or higher. In the above equation M represents an alkali metal, such as sodium.

This synthesis is illustrated by the following example.

EXAMPLE 3 Two and a half moles of O=C(PO Na dissolved in 3 liters of water at pH 10.8, was subjected to hydrogen at a pressure of 600 pounds per square inch for 8 hours at 100 C. in the presence of Raney nickel catalyst. After this period of heating, a P nuclear magnetic resonance spectrum revealed that all of the CDP starting material (absorbing at 0.0 p.p.m. relative to 85% H PO reference) had disappeared. The solution was titrated to a pH of 5, a small amount of ethylenediaminetetraacetic acid was added to complex the Ni++ ions in solution, and methanol was added. Disodium methanehydroxydiphosphonate, HOCH(PO NaH) was isolated in 73% yield, and identified by P nuclear magnetic resonance spectra and elemental analysis.

(3) Builders.While any water soluble alkali metal or ammonium or substituted ammonium salt form can be used as a detergency builder according to this invention, the trisodium salt, the tetrasodium salt, and trisodiumtetrasodium mixtures are the preferred forms. Mixtures of the tetrasodium and trisodium salts give a pH in water solution from about 8 to 12. Each of the lesser neutralized forms such as monosodium and disodium derivatives or the free acid have builder capacity comparable to the trisodium and tetrasodium salt forms, provided that additional alkali is added, if necessary, to adjust the pH of the washing solution to be within about 8 to about 12. The compounds of this invention perform best, as builders, in this pH range. The standard alkaline materials can be used for this purpose when necessary, such as alkali metal silicates, phosphates, borates and carbonates. Free alkali materials such as sodium and potassium hy droxides can also be used.

Detergents which may be built with CDP include ani onic synthetic detergents, nonionic synthetic detergents, ampholytic synthetic detergents, and zwitterionic synthetic detergents, singly or in combination. The chief advantage of CDP as a builder is its surprising stability 6 to hydrolysis in aqueous solution. This stability is unexpected in view of the instability of carbonylmonophosphonate salts (i.e., compounds of the structure where R is an alkyl radical or an aryl radical, and M is a cation, for example an alkali metal salt).

What is claimed is: 1. Compounds having a formula I a 2 i P aMz in which each M is sodium, potassium, ammonium or tetramethylammonium.

2. Sodium carbonyldiphosphonate.

References Cited UNITED STATES PATENTS 2,599,761 6/1952 Harmon et al. 260932 3,051,740 8/1962 Abramo et al. 260502.4 3,110,727 11/1963 Toy et al. 260502.4 3,214,454 10/1965 Blaver et al 260502.4 3,256,370 6/1966 Fitch et al. 260502.4 3,271,306 9/1966 Capriati et al 260502.4 3,297,578 1/ 1967 Crutchfield et al. 260502.4

FOREIGN PATENTS 1,026,366 4/1966 Great Britain.

OTHER REFERENCES Patai: The Chemistry of the Carbonyl Group (1966), QD 305.A6P3, pp. 177 to 133.

Kabachnik et al. (I): Chem. Abstracts, vol. 51 (1957), C015. 10366, 10367, QDlASl.

Kabachnik et a1. (II): Chem. Abstracts, vol. 53 (1959), col. 6988, QD1A5l.

BERNARD HELFIN, Primary Examiner J. E. EVANS, Assistant Examiner US. Cl. X.R. 

